Fullerene shell tube and process for producing the same

ABSTRACT

Fullerene whiskers or fibers obtained by a liquid-liquid interfacial precipitation method are heat-treated in vacuum or in a gas atmosphere at a temperature of from 500 to 1,000° C. to form a fullerene shell tube which can be used in wide applications such as field emission devices, gas filters, hydrogen storage materials and catalyst supports in energy, catalyst and semiconductor industries.

TECHNICAL FIELD

The invention of this application relates to a fullerene shell tubewhich can be used in wide applications such as field emission devices,gas filters, hydrogen storage materials and catalyst supports in variousindustries such as energy, chemical industries, electronics andsemiconductors, and a process for producing the same.

BACKGROUND ART

Although the presence of a fullerene was experimentally proved byresearchers abroad in 1985, its structural model had been already knownin Japan in 1970. Thus, Japan has always led the world in studies offullerenes. As a typical fullerene, C₆₀ has been known. Variousfullerenes such as C₇₀, C₇₆, C₇₈, C₈₂, C₈₄, C₂₄₀, C₅₄₀ and C₇₂₀ otherthan C₆₀ have been known. The technology in the field of fullerenes hasbeen progressed very quickly, and new fullerene compounds have beenintroduced one after another. Recently, a process in which a shellstructure comprising amorphous carbon derived from fullerene is formedby heat-treating crystals of typical fullerene C₆₀ in vacuum (non-PatentDocument 1), a process in which fullerene whiskers (carbon filaments)are produced by a liquid-liquid interfacial precipitation method, andthe like have been proposed by the inventors of this application (forexample, Patent Document 1 and non-Patent Documents 2 and 3).

Meanwhile, as a tube having a carbon wall structure, a carbon nanotubehas been known.

This carbon nanotube has a structure in which a graphite sheet iscylindrically rolled up. Unlike such a structure of the carbon nanotube,a structure of a fullerene shell tube derived from a fullerene whisker(FW) or a fullerene nanowhisker (FNW) having a three-dimensionalperiodical structure in which symmetry of fullerene needle crystals orthe like is defined by a space group has been imagined. It has been sofar known that a fullerene shell is formed by heat-treating crystals ofa fullerene, but a tubular fullerene shell (hereinafter referred to as afullerene shell tube) or a process for producing the same has been todate utterly unknown.

Patent Document 1: JP-A 2003-1600

non-Patent Document 1: H. Sakuma, M. Tachibana, H. Sugiura, K. Kojima,S. Ito, T. Sekiguchi, Y. Achiba, J. Mater, Res., 12(1997)1545.

non-Patent Document 2: K. Miyazawa, Y. Kuwasaki, A. Obayashi and M.Kuwabara, “C60 nanowhiskers formed by the liquid-liquid interfacialprecipitation method”, J. Mater, Res., 17[1](2002)83.

non-Patent Document 3: Kunichi Miyazawa “C70 Nanowhiskers Fabricated byForming Liquid/Liquid Interfaces in the Systems of Toluene Solution ofC70 and Isopropyl Alcohol”, J. Am. Ceram. Soc., 85[5] (2002) 1297.

In view of the structure, it is expected that the fullerene shell tubecan be used in applications such as hydrogen storage materials, catalystsupports, new semiconductors, field emission materials and fuel cellelectrode materials. However, as stated earlier, the fact is that aprocess for producing a fullerene shell tube and various possibilitiesof this fullerene shell tube structure have been unknown.

Accordingly, the invention of this application aims to provide afullerene shell tube expected as a new functional material and a processfor producing the same.

DISCLOSURE OF THE INVENTION

In order to solve the foregoing problems, the invention first provides aprocess for producing a fullerene shell tube, which comprisesheat-treating a fullerene whisker or fiber at a temperature of from 500to 1,000° C.

Second, it provides the process for producing the fullerene shell tube,wherein the fullerene is C₆₀ fullerene, a higher-order fullerene havingthe carbon number of 70 or more, a metal-containing fullerene orfullerene derivatives.

The invention of this application third provides a fullerene shell tubein which a diameter is in the range of from 10 nm to 100 μm, and alength is 100 nm or more.

Fourth, it provides the fullerene shell tube, wherein the tube wallcomprises crystalline carbon or amorphous carbon.

Fifth, it provides the fullerene shell tube, wherein the end of the tubeis closed or open.

Sixth, it provides the fullerene shell tube, wherein the inside ishollow, or the inside is filled.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a transmission electron microscope (TEM) photograph of afullerene shell tube produced by heating a fullerene nanowhisker invacuum at 600° C. for 30 minutes.

FIG. 2 is a transmission electron microscope (TEM) photograph of afullerene shell tube produced by heating a fullerene nanowhisker invacuum at 700° C. for 30 minutes.

FIG. 3 is a transmission electron microscope (TEM) photograph of afullerene shell tube produced by heating a fullerene nanowhisker invacuum at 600° C. for 30 minutes.

FIG. 4 is a transmission electron microscope (TEM) photograph of afullerene shell tube with a filling tissue thereinside which tube isproduced by heating a fullerene nanowhisker in vacuum at 600° C. for 30minutes.

BEST MODE FOR CARRYING OUT THE INVENTION

The invention of this application has the foregoing characteristics. Theembodiment thereof is described below.

In the invention of this application, the fullerene shell tube isproduced by heat-treating various fullerene whiskers or fibers at thetemperature of from 500 to 1,000° C. In this instance, the fullereneincludes not only typical C₆₀ whiskers or fibers, but also whiskers orfibers of higher-order fullerenes having the carbon number of 70 ormore, metal-containing fullerenes and further various fullerenederivatives which have been so far known.

These various fullerene whiskers or fibers to be heat-treated can beprepared by a so-called liquid-liquid interfacial precipitation method,as proposed by the inventors of this application in the foregoing PatentDocument 1 or the like, which comprises dissolving a fullerene in afirst solvent such as toluene, xylene, benzene, hexane, pentane or CS₂,adding to the solution a second alcoholic solvent which has a lowersolubility than that of the first solvent and is not mixed therewithimmediately, such as pentanol, butyl alcohol, isopropyl alcohol,n-propyl alcohol, methanol or ethanol, and precipitating whiskers orfibers which are needle crystals of the fullerene in the liquid-liquidinterface of the first and second solvents while keeping the mixture atnear room temperature (from 3° C. to 30° C).

The heating at the temperature of from 500° C. to 1,000° C. is conductedin vacuum or in a gas atmosphere. In this case, it is considered that adegree of vacuum is a pressure of 1 Pa or less, the gas atmosphere is anoxygen partial pressure of 10⁻¹ Pa or less, and the like. An inert gassuch as argon may be present.

The invention is thus illustrated more specifically below by referringto Example. Of course, the invention is not limited by the followingExample.

EXAMPLE Example 1

According to a liquid-liquid interfacial precipitation method, 30 ml ofisopropyl alcohol is first gently added to 30 ml of toluene saturatedwith fullerene (C₆₀) having a purity of 99.5%. The solution is kept atroom temperature (from 15° C. to 21° C.) for approximately 50 hours toproduce a fullerene nanowhisker. Subsequently, the resulting fullerenenanowhisker is retained in vacuum at 600° C., and heat-treated for 30minutes to produce a fullerene shell tube having a wall of amorphouscarbon.

FIG. 1 is a transmission electron microscope (TEM) photograph of theresulting fullerene shell tube. As shown in the photograph, thefullerene shell tube made of the fullerene nanowhisker has ananometer-order diameter, and it is confirmed, as shown by the arrow,that a polygonal wall structure is present by reflecting the crystalhabit surface of the original fullerene nanowhisker. Incidentally, thecrystal habit here referred to indicates characteristics of the size andthe form of the crystal.

FIG. 2 is a transmission electron microscope (TEM) photograph of afullerene shell tube wall produced by heating a fullerene nanowhisker invacuum at 700° C. for 30 minutes. From the transmission electronmicroscope photograph, it is confirmed that the fullerene shell tubewall comprises amorphous carbon and has a thickness of approximately 30nm.

FIG. 3 is a transmission electron microscope (TEM) of the fullereneshell tube wall.

As shown in FIG. 3, it is observed that the end of the fullerene shelltube is sometimes closed. It is further observed, as shown in FIG. 4,that the inside of the fullerene shell tube has a filling tissue.Amorphous carbon is presumably filled during formation of the shell tubestructure.

Of course, the invention of this application is not limited to theforegoing embodiment and Example. Regarding the details, variousembodiments are possible.

INDUSTRIAL APPLICABILITY

According to a process for producing a fullerene shell tube in the firstinvention of this application, a fullerene shell tube useful as afunctional material in wide applications such as field emission devices,gas filters, hydrogen storage materials and catalyst supports in energy,catalyst and semiconductor industries.

According to a process for producing a fullerene shell tube in thesecond invention, the foregoing effect is obtained, and it is furtherpossible to select a fullerene which can be used advantageously.

According to the third invention, a fullerene shell tube having aspecific size is provided.

According to the fourth invention, the foregoing effect is obtained, andfurther a shape of a carbon wall constituting the fullerene shell tubeis specified.

According to the fifth invention, the foregoing effect is obtained, andfurther a structure of an end of the fullerene shell tube wall isspecified.

According to the sixth invention, a state of the inside of the fullereneshell tube is specified.

The fullerene shell tube obtained in the invention of this applicationis useful as a new functional material in wide applications such asfield emission devices, gas filters, hydrogen storage materials andcatalyst supports in various industries such as energy, chemicalindustries, electronics and semiconductors.

1. A process for producing a fullerene shell tube, which comprisesheat-treating a fullerene whisker or fiber at a temperature of from 500to 1,000° C. in vacuum of 1 Pa to form a fullerene shell tube which hasan amorphous carbon wall and whose inside is hollow.
 2. The process forproducing the fullerene shell tube according to claim 1, wherein thefullerene is C₆₀ fullerene, a higher-order fullerene having the carbonnumber of 70 or more, a metal-containing fullerene or fullerenederivatives.
 3. A fullerene shell tube in which a diameter is in therange of from 10 nm to 100 μm, a length is 100 nm or more, the tube wallcomprises amorphous carbon, and the inside is hollow.
 4. (canceled) 5.The fullerene shell tube according to claim 3, wherein the end of thetube is closed or open.
 6. (canceled)